diff --git a/redwood-protocol-host/src/commonMain/kotlin/app/cash/redwood/protocol/host/HostProtocolAdapter.kt b/redwood-protocol-host/src/commonMain/kotlin/app/cash/redwood/protocol/host/HostProtocolAdapter.kt
index e7a01e1434..50db1fc4b0 100644
--- a/redwood-protocol-host/src/commonMain/kotlin/app/cash/redwood/protocol/host/HostProtocolAdapter.kt
+++ b/redwood-protocol-host/src/commonMain/kotlin/app/cash/redwood/protocol/host/HostProtocolAdapter.kt
@@ -52,8 +52,8 @@ public class HostProtocolAdapter<W : Any>(
   factory: ProtocolFactory<W>,
   private val eventSink: EventSink,
 ) : ChangesSink {
-  private val factory = requireNotNull(factory as? GeneratedProtocolFactory<W>) {
-    "Factory ${factory::class} was not generated by Redwood or is out of date"
+  private val factory = when (factory) {
+    is GeneratedProtocolFactory -> factory
   }
 
   private val nodes = mutableMapOf<Id, ProtocolNode<W>>(